The invention relates to an adjustable steering column for a motor vehicle with a clamping arrangement, in the opened state of which the steering column is adjustable and in the closed state of which the set position of the steering column is fixed, and which comprises an actuation lever and a clamp bolt having a longitudinal axis. A clamping part for opening and closing of the clamping arrangement is rotatable by the actuation lever about the longitudinal axis of the clamp bolt, and is disposed on the clamp bolt or is implemented integrally with it. The invention further relates to a method for securing an actuation lever of a clamping arrangement of an adjustable steering column for a motor vehicle on a clamp bolt and/or clamping part of the clamping arrangement, in the opened state of which the steering column is adjustable and, in the closed state of which the set position of the steering column is fixed and for the opening and closing of which the clamping part is rotatable by the actuation lever about the longitudinal axis of the clamp bolt.
Adjustable steering columns for motor vehicles are known in many different implementations. In a conventional implementation, the adjustability of the steering column is released or blocked by turning of an actuation lever about the longitudinal axis of a clamp bolt. A clamping part is rotated by the actuation lever about the axis of the clamp bolt, and the clamping part is formed, for example, by a cam disk cooperating with a cam follower disk. To secure the adjustment in the closed state of the clamping arrangement actuated by the actuation lever, friction faces, tightened against one another by the clamping arrangement for the securement under force closure, can for example be provided, or toothings joined by the clamping arrangement for a securement under form closure. The adjustability can refer to the axial direction of the steering column and/or the inclination or height adjustment.
An adjustable steering column is disclosed, for example, in DE 101 41 551 A1. The clamping arrangement comprises an actuation lever, a clamp bolt on which the actuation lever is turnably disposed, a clamping piece, also turnably disposed on the clamp bolt, in the form of a cam disk, and a cam follower disk cooperating therewith. The actuation lever is connected under form closure with the clamping piece through pins of the clamping piece which engage into recesses of the actuation lever. This form closure, for one, reliably ensures the positioning of the actuation lever and, for another, tranfers the force necessary for the opening and closing of the clamping arrangement from the actuation lever onto the clamping piece. To improve the protection of the motor vehicle driver in the event of a vehicle crash, a lever portion of the actuation lever is connected through a tearing mechanism with a bearing portion of the actuation lever via which the turnable bearing on the clamp bolt takes place. Through this mechanism, the lever portion can become detached from the bearing portion in the event of a crash.
In the adjustable steering column disclosed in EP 1 747 966 A2, the actuation lever is also connected under form closure with a cam disk, the cam disk including a rectangular projection pressed into a rectangular recess of the actuation lever. A cam follower disk, with respect to which the cam disk is turned by the actuation lever for opening and closing the clamping arrangement, comprises stops for the cams of the cam disk which, in the event of a crash, can be bent over. The cam disk, in the event of a crash, can thereby be further turned with respect to the cam follower disk whereby the turning of the actuation lever is also enabled in order to improve the driver protection in the event of a crash.
WO 2009/141045 A2 discloses an integral implementation of a clamping part, implemented in the form of a cam disk, with a clamp bolt of a clamping arrangement which serves for securing in position an adjustable steering column for a motor vehicle. On the side opposing the cam, a form contour is realized on the clamping part and the actuation lever is realized with an indentation having a corresponding form whereby a connection under form closure with the actuation lever is established. During the turning of the actuation lever, the clamping part, integrally implemented with the clamp bolt, is also turned simultaneously therewith.
Of disadvantage in these prior known steering columns is that the rotational orientation of the actuation lever with respect to the clamping part is defined at the outset, and potential tolerances of the structural parts lead to changed rotational settings of the actuation lever for the opened or closed state of the clamping arrangement. The assembly can also be complex depending on implementation if the actuation lever must be preassembled with the clamping part and the assembly must subsequently be mounted into the steering column assembly.
Further proposals for improving the protection of the vehicle driver in the event of a vehicle crash are disclosed in WO 03/018 384 A1 and U.S. Pat. No. 7,125,046 B2. In the first document, the actuation lever is implemented as a deformation element such that it is deformable by an impact with the consumption of energy. U.S. Pat. No. 7,125,046 B2 shows an adjustable steering column in which, in the event of a crash, the jacket tube can become shifted in the direction toward the vehicle front.